This invention relates to the structure of a rectifier device which employs a flat type element.
For example, a brushless excitation apparatus is such that an A.C. exciter and a rotary rectifier device rotate coaxially, and it supplies direct current without using a slip ring as the excitation apparatus of any of small-sized to large-sized A.C. machines. The rotary rectifier device requires components such as a semiconductor element (usually a diode), radiating fins and a fuse, and a large number of members including predetermined connectors and supporters. In addition, it needs to endure a great centrifugal force during the rotation and to be packed in the smallest possible structure.
A prior-art rotary rectifier device employing a flat type element and for use with a large-sized exciter has a structure as shown in FIGS. 1A and 1B. These figures illustrate one module of the prior-art rectifier device. Numeral 1 designates a flat type semiconductor element, which is held between radiating fins 2 and 3. Numeral 11 indicates a capacitor, and numeral 4 an A.C. side terminal. Numeral 5 indicates a leaf spring which is mounted on the radiating fin 3 by a bolt 12 and which exerts a pressure on the semiconductor element 1 through a spacer 10. Insulating struts 6 support the leaf spring 5 unitarily with the radiating fin 3 and the semiconductor element 1. Shown at numerals 7 are D.C. side terminals. A fuse 8 is connected in electrical series with the semiconductor element 1. The assembly made up of the semiconductor element 1, radiating fins 2 and 3, capacitor 11, etc., is fixed to a wheel 9 through an insulator 14 by an insulating bolt 13.
The flat type semiconductor element 1 has the radiating fins 2 and 3 disposed on both its surfaces, and is subjected to a proper contact pressure. This brings forth the advantages that the semiconductor element can conduct a greater current than a stud type diode having heretofore been utilized, and that the device can be made smaller in size. In order to fully exploit the advantages, the prior art adopts the structure wherein the semiconductor element 1 and the radiating fins 2 and 3 on both the sides thereof are sandwiched between the capacitor 11 and the spring 5 and wherein they are supported by the insulating struts 6 collectively and are held by a spring pressure which is adjusted by the thickness of the spacer 10 inserted centrally of the spring 5.
Such a prior-art module structure has a great cooling capability, and is practical. Since, however, the semiconductor element is not completely enclosed, it is liable to become dirty, which may lower its dielectric strength. Another disdvantage is that the insulating struts protrude, so that the windage loss due to rotation is heavy.